The present invention relates to a solid-state imaging apparatus having a solid-state image pickup element used for a video camera, and relates in particular to a solid-state imaging apparatus having a correction device for correcting a signal that is output by a solid-state image pickup element for a defective pixel.
FIG. 10 is a diagram showing the configuration of a conventional solid-state imaging apparatus having a defective pixel correction function, which is disclosed in Japanese Patent Publication No. Hei. 5-41868. In the conventional solid-state imaging apparatus, image data is detected through a lens 101 by a frame-reading image pickup element. The obtained image signal is pre-processed by a pre-processor 103, and the resultant signal is converted into a digital image signal by an A/D converter 104.
This digital image signal is delayed one horizontal scanning period by a 1 H delay circuit 105, and is further delayed one horizontal scanning period (the total of two horizontal scanning periods) by a 1 H delay circuit 106. The digital image signal output by the A/D converter 104, the digital image signal delayed one horizontal scanning period, and the digital image signal delayed two horizontal scanning periods are transmitted to a color signal processor 107 to generate a color signal, and are also respectively transmitted, for filtering, to digital low-pass filters 108, 109 and 110.
The three image signals that have been filtered are transmitted to a defective pixel detector 111, and to detect a defective pixel, are compared with a threshold value 112. A defective pixel correction circuit 113 receives these three filtered image signals and a defective pixel detection signal obtained by the defective pixel detector 111, corrects the pixel signal for the defective pixel, and outputs the image signal to a luminance signal processor 114, which thereafter generates a luminance signal.
The conventional defective pixel detector 111 extracts, from the image signal, pixel data for a pixel for which a determination is to be made and adjacent, peripheral pixels, and performs for these pixel data an addition/subtraction procedure or a comparison to calculate a projection value (the difference between the pixel data for the target pixel and the pixel data for the peripheral pixels). The defective pixel detector 111 then compares the projection value with the threshold value 112 to determine whether the target pixel is defective.
From among the pixel data that are read by the frame-reading solid-state image pickup element 102, the conventional solid-state imaging apparatus adds data for two vertical pixels that are output by the filters 108, 109 and 110, and also adds data for two horizontal pixels to obtain a luminance signal. Then, the defective pixel correction device employs peripheral pixel data to correct the pixel data for the pixel that is determined to be defective. Therefore, the effect produced by the defective pixel spreads to the pixel data for the peripheral pixels, and it is impossible for the defective pixel to be detected correctly and the pixel data therefor to be corrected.